Process of obtaining alkali-metal compound from silicates.



PROCESS 0F OBTAINING ALKALI METAL COMPOUND FROM SILICATES.

APPLICATION FILED FEB. 18.1915.

Patented Oct. 10, 1916.

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WALTER AUGUST SCHMIDT, .OF LOS ANGELES, CALIFORNIA, ASSIGNOR TO INTER NATIONAL PRECIPITATION COMPANY, OF LOS ANGELES, CALIFORNIA, A CORPO- RATION OF CALIFORNIA.

PROCESS OF OBTAINING ALKALI-METAL COMPOUNDFROM SILICATES.

'aeoogeea Specicati'on of Letters Patent.

Application led February 18, 1915. Serial No. 9,066.

To fzZZ'wwm t may concern.'

Be it known that I, WAL'I'ER AUGUST SCHMIDT, a citizen of the United States, residing at Los Angeles, in the county of Los Angeles and State of California, have inveted a new andlseful Process of Obtaining Alkali-Metal Compounds from Silivcates, of vvhichqthe. follovving is a specification. When potash-bearing mineral silicates such as feldspar and similar materials arei -subjected to the action of heat under suitable conditions, and in the presence of lime or equivalent alkaline earth, some of the potash is liberated in the form of a volatile compound, which passes 0H and may be recovered by suitable means. I have found that under some conditions the presence -of sulfur dioxid and oxygen in Contact with the material or with the volatile potassium compound, is of advantage in increasing the amount of potash obtained from the mineral.` The collection or recovery of the potassium compound when driven 0E inthis manner, is a matter of some diculty. The potassium compound isl liberated from th@ mineral at a high temperature and condenses to solid' state at a temperature Which is considerably above any temperature that can be sustained by bag lters. The fume produced by the condensed particles of potassium compound is so 'fine that its complete 'recovery in settling chambers is out of the question. Moreover, under conditions of practice the gases carrying the potassium compound, either as vapor. or suspended matter, also, in general, contain a considerable amount of kother material in the form of dust or fume whchconstitutes an impurity when Vcollected with the potassium compound. A A

An' important object of my process 'is to i 'provide for effective separation of the potassium compound from such impurities.

Another object of my invention is to pro vide a process whereby the fumes containing potassium compound can be precipitated pound from other materials present in the gases.

Another object of the invention .is to enable the potassium compound to be precipitated at a temperature which does not rev quire undue cooling of the gases containing the same. and to avoid the expense of cooling the gases to a relatively 10W temperature, it is desirable to precipitate the potassium compound at a temperature as little as possible below the temperature -of condensation thereof, and my proce'ss provides for such precipitation at a relatively high temperature.

My invention is particularly applicable in connection with cement manufacture, the method of .precipitation used by me being especially adapted to treat the great volumes of stack gases, carrying extremely line fumes, which are producedin such manufacture, in such manner as to`recover a large proportion of the notash content of the materials used, with a minimum of expense and of cement, the potash being in that case a by-product of such production. Fig. 2 is a section on line 2 2 in Fig. 1. Fig. 3 is a vertical section of a form of apparatus suitable for applying my process to the recovery of potash as a main product.

Referring to Fig. l, the apparatus therein "short/n comprises a kiln 1 for heating the mixture of materials containing the constituent to be separated, said kiln being shown as a cement kiln for burning cement mixture to form clinker.' rlhis kiln is h eated by a burner 2, which, in this embodiment of the invention isadapted to furnish not only the heat required for burning the l to a treater 'or electrical` precipitator, 5,

adapted to burn fuel oil containing a iconsiderable proportion of 1 sulfur. an @una eue 4 leads from the kan Patented Cet. it, is

In order to maintain the draft v invention in connection with the production comprising a plurality of 'sections orsets, 5',

through which the gas from the passes successively, `so as vto be subjected to progressive cooling action .,therein, said treater pound tends to collect in the later bins of section comprising a series of sets of disthe series. charge electrodes 7 and collecting electrodes bins or receptacles, 11, is then compara- 8 arranged within a casing .9, adapted to tively poorin potash in the bins nearer the conduct the gas Vfrom the liue 4 successively kiln and the potash content increases probetween the sets `of electrodes and to disgressively in the bins more remote from the charge the gas through a flue 10. ASeparate kiln, so that in certain ofthe bins, for exreceptacles or bins 11 are provided for reample, thelast bins of the series, the dust ceivin the precipitates from the respective contains suiiicient potash to give it commersets o electrodes. Means are provided for cial value as a fertilizer, or for otherl purapplying unidirectional current of high poposes.

tential diierencerto said electrodes, com- In carrying out my process as above d'eprising, for example, a step-up transformer scribed, I have used a clay aggregate con- 12. havingl its primary winding connected taining about 2O per cent. of feldspar, the to an alternating current supply circuit 17, potash of the feldspar constituting about The material collected in the.

and having its secondary' winding connected .72 per cent. of such clay aggregate. The

through a rectifier 13 to the discharge elecfuel oil used in the process contained about trodes 7 of the' treater, by wire 14, and to 1.2 per cent. sulfur. The potash content in ground by wire 15; the collecting electrodes the bins was about 1 per cent. in the lirst 8 being also grounded, a`s at 16. The disbins of the series and about 3 per cent. in charge electrodes 7, may be wires, and the the last bins of the series, and averaged collecting electrodes 8 may be plates or about .2 per cent.y screens. The dust collected in the several bins may My invention is carried out in this apbe removed, and in case it contains sulicient paratus as follows: The cement mixture used potash to render it commercially valuable, comprises a lime aggregate and a clay ag-' as, for example, in the case lof the later bins gregate, containing more or less potash, (for of the series, it may be sold 'as fertilizer or example, as a eldspar constitutent); said t, for other purposes, or the potassium comaggregates being ground-and mixed together fpoundv may be leached from said dust with in the usual manner. Such cement mixture water. Any of the dust which is not suliiis supplied to the' kiln 1, through supply ciely rich in potash to make it commermeans 3, and in passing through the kiln, is cially valuable for its potash content may heated by the action of burner2, so as to be returned to the kilnfl along with additional form cement clinker. In carrying out my raw mix to form part of the cement mixture. process I have -used a fuel oilcontaining a Moreover, any desired part of the dust so considerable percentage of SO2. The gases lcollected may be concentrated to a condipassing from the burner passing in contact tion of greater richness in potash; for exwith the highly heated the outlet 4 'contain a considerable quantity 5 potassium compound.

potassium bearing ample, by passing such dust through the material in the mixture, react therewith to Vkiln 1, or a similar kiln, so that the same form a compound (potassium sulfite, or operation takes lplace on the dust as above sulfate) which is volatile at the temperadescribed for the cement mixture, with the ture of the gases in the kiln and is therefore -result that potassium compound in the dust volatilized and carried olf by the current of so supplied to the kiln is volatilized by the gas through the kiln. heat of the kiln, and the other constituents The gases passing from the kiln through of such dust, being relatively non-volatile,

are'carried over to the treater in less proof dust or Enely divided' solid matter portion than such potassium compound, so pended therein, aswell as the vapor of-such that on condensation of such compound by As'` the gases are cooling in the treater, and precipitating the cooled by radiation and conduction of condensed particles by electrical action in lheat therefrom, throughthe walls of the the treater there is collected in the treater apparatus, the potassilm compound' is bins a material whichis comparatively rich condensed from the form of vaporA to in potash. Bythis means I have been able, the form of a cloud of particles, such par- -using the cement constituents above de- A ticles being suspended in the gas and passmg along with the other suspended matter in the gas, through theprecipitator 5.V As

' the gases pass through the precipitatorthe action of the electrical discharge between theelectrodes thereof` causes precipitation of the suspended matter, and in this operation the coarser particles are first precipitated. and the finer particles,

consisting largely of the potasslumcompound are precipltated more slowly, se that such comeffective separation of the potash is secured, as above indicated, resulting in a potash product of commercial value.

In applying the process to the recovery of potash as a main product, 'I may also use the apparatus shown in Fig. 1, or I may use the apparatus shown in Fig. 3, comprising a roaster or furnace 20, adapted to roast py-'- 4heater 24 may be provided with burner means for maintaining the same at the proper temperature and may have means 31 for admission of air and means 32 for supply of mineral thereto. An electrical precipitator 22 is provided for precipitating the dust or suspended solid matter coming from the' roaster 20, said precipitator being located at any suitable point in the apparatus, for example, as shown between the roaster 20 and the heater 24; or it may be connected to the outlet of the said heater. The gas" passing from -said heater, and from which the suspended matter has been removed by the action of said precipitator, is led by piping 27, 28, through a cooler 26, to an electrical precipitator 29,' which discharges the gas through a stack 30. Each of the electrical precipitators 22 and 29 may be of any suitable type, kfor example, of the type shown, comprising discharge electrodes 33 formed as fine wires, hung axially in vertical pipes 34, acting as collecting electrodes, .bins 35 being provided below said .vertical pipes for receiving Athe precipitated material, and headers 36 and 37 being provided at the lower and upper ends of said pipes for conducting the' gases to and from thesame. The discharge electrodes 33 are connected to the high tension side A14, of a uni-directional high tension current circuit and the collecting electrodes 34 are grounded as at 16. i

My process mayV be carried out in the above described apparatus as follows: The gases containing sulfur dioxid are drawn frointhe roaster 20, by the action of natural or forced draft, andv caused to pass through the heater 24, and the potash bearing mineral, such-v as feldspar, finely ground and mixed with lime is also supplied to said heater so as to be exposed to contact with such gases, the heater being maintained at a suitable temperature, for example, about 1000 degrees C., and air beingadmitted if necessary, so that the potash in the com# pound is acted upon to form a compound which is volatile at the temperature of the heater and is therefore driven ott' from the mineral and passes off with thecurrent of gas. Any :lust or suspended matter carried over from the roaster 20 is removed from the gas by the action of precipitator 22, either before or 'after the gas has passed through the heater 24. If desired, an additional precipitator may be interposed between the heater 24 and the cooler 26, to receive any solid matter carried over from the heater. The gases then pass through the cooler 26 wherein their temperature is reduced sufficiently to fully condense the potassium compound, forming a cloud of particles suspended in the gas, and this suspended material containing. the'potassium compound is then cipitator 29.

Thev furnace 20, instead of being a fur \nace or roaster for production of sulfur dioxid, may be a smelting or other furnace in whichsulfur dioxid is formed as a waste`V precipitated in the pre` product, and in such case the main object of the invention may be the elimination of the sulfur dioxid from the waste gases of such a furnace. In such case the process may be carried out as above described, except that vthe produced compound containing potas l sium sulfite or sulfate or both, may be discharged as a waste product, with or without precipitation.

I have described my process as applied to utilization of potassium in minerals such as feldspar. My invention is however applicable to any mineral containing an alkali capable of .reacting with sulfur dioxid in the manner described. Moreover, in place' of lime as a reagent, I may use any base capable of acting in the same manner in the stated reaction. I have found elec-l trical precipitation to be the most effective method of removing the suspended material from the gases, as it enables the fumes to vbe collected at temperatures not materially below ordinary stack temperatures,and at moderate expense for construction and operation of plant, notwithstanding the ex'- treme ineness of the fumes and the great volumes of gas involved. The action of thev sulfur dioxid and voxygen contained in the gases is of value in increasing the amount of potassium compound, under the conditions above set forth, either by facilitating the formation of a volatile compound from the feldspar, or by facilitating the condensation of the already volatilized potassium compound, according to the conditions der which the process is carried out. What I claim is:

1. The process of recovering potassium -K compound from feldspar and similar minerals, which consistsin subjecting the same to heat in the presence of an alkaline earth and of hot gases in such manner as to volatilize potassium compound from said mineral, drawing oi such .hot gases containing such potassium compound, such and potassium compound to condense to form suspended particles in the gases, and subjecting the gases to the action of an electric field` to precipitate the suspended particles of potassium compound from the gases.

'2. The process of recovering potassium Vcompound from feldspar and similar -min-V erals, which consists in subjecting the same 'to heat in the presence of an alkaline earth and hot gases, in such manner as to volatilize and remove potassium compound from such mineral, drawing off such hot gases containing suchpotassium compound, causing such potassium compound to condense to form suspended particles in the gases, subjecting the gases while still at a high temperature to the action of an electrical field to precipitate thesuspended particles of potassium compound from the gases. l

3. The process of removing potassium compound from feldspar and similar minerals, which consists in subjecting the same to high temperature in thepr'esence of an.

alkaline earth and vof hot gases, containing sulfurdioxid in such manner as to volatilize Aand remove potassium compound from said mineral, drawing olil such hot gases containing such potassium compound, condensing the potassium compound to form suspended particles in the gases, and subjecting the gases to the action of an electrical lield Vto precipitate such suspended particles therefrom.' e 4 4. The process of treating mineral silicates containing potassium for recovery of potassium compound therefrom, which consists in passing,l in contact with such sili-V cates and in the presence of lime, hot gases containing sulfur dioxid, insuch manner as to volatilize and carry oil potassium com-` pound from said mineral silicates, causing said gases to cool so as to condense the potassium compound, and subjecting the gases to the action of an electrical field to precipitate the condensed potassium compound therefrom. s

5. The process of treating mineral silicates containing potassium for recovery ofpotassium therefrom, which consists in passing, in contact with such mineral silicates, gases heated-' to a suiicient temperature to volatilize and-icarrv o potassium compound from such mineral silicates, and subjecting the gases to a plurality oi s uccessive precipitating actions in 'elect `fields to first precipitate from the gass'dust' and other impurlties carried over with theygases and.: to then precipitate .gportions ofv potassium compound. L

6. The process of 'treating mineral. sili vcates containing potassium, which in passing, in contact with such mineral -si]i cates, together 'with lime, gases at suiiicient temperature and at 4 suiicient velocity to carry olf potassium compound in the form` of Vvapor together with the finely divided mineral matter Suspended in said gases, progreively cooling the gases toa temperature sulicient to condense such potassium compound, and subjecting the gases while being progressively cooled to the successive action of a plurality of electrical fields to precipitate successively the finely divided mineral matter carried over by the gases and successive portions of the condensed potassium matter andthe condensed potassium compound.

V8. The process of treating mineralvsilicates containing potassium for recovery of potassium compound therefrom, which consists in mixing said silicates with lime, passing h'ot gases in contact with the said mineral silicate and lime, said gases being at suicient temperature to cause volatilization of potassium compound, drawing oif the gases from the mineral silicate together with y the volatilized potassium` compound and finely dividedmineral matter taken up by` the gases, and subjecting the gases to a plurality of precipitating actions to separate portions relatively rich in potassium com pound from portions relatively poor in potassium compound'.

9. The process of treating mineral silicates containing potassium for recovery of potassium compound therefrom, which consists in mixing said silicates with lime, passing hot gases in contact with thesaid mineral silicate and lime, said gases being at suflicient temperature to cause volatilization of potassium compound, drawing' oli the gases from the mineral silicate together with the volatilized potassium compound and finely divided mineral matter taken up by the gases', and subjecting the gases to a plu- A rahty of percipitating actions to separate portions relatively richY in potassium compound from portions relatively poor in potassium compound, subjecting said' portions relatively rich in potassium compound, to theaction of heat to volatilize potassium compound therefrom, and precipitating the potassium compound so volatilized.

10; The process of recovering alkali metal l.

compounds from mineral silicates, which consists in subjecting the silicates to heat in the presence ofan alkaline earth and of hot gases, in such manner as to volatilize alkali metal compound from such silicate, drawing off the hot gases containing such alkali metal comp'ound, causing such alkali metal com- 'pound to condense to form suspended par- 1Q in subjecting such silicates to heat in the presence of an alkaline earth and of hot gases, in such manner as to v olatilize alkali metal compound from the silicate, drawing oil"` the hot gases containing such alkali metal compound, causing such alkali metal comze -relatively rich in alkali metal compound 25y from portions relatively poor in alkali metal compound.

In testimony whereof I have hereunto set my hand, at Los Angeles, California, this 6th day of February 1915.

WALTER AUGUST SCHMIDT.

Witnesses:

A. P. KNIGHT, WM N. DREW. 

